In the distant future, the human race is on the brink of destruction. Mankind, which now drifts in space aboard a massive, technologically-advanced base known as Avalon, is poised to launch one final, desperate attack against its enemy, the alien race Hideauze. It’s during this battle that Ledo, a mecha pilot, is thrown into a wormhole and sent to an unfamiliar place: Earth, the lost birthplace of humanity said to have turned to ice long ago. Having been saved by the inhabitants of the Gargantia, a fleet of ships that traverses the now-flooded planet, Ledo must come to terms with these primitive people with their backwards language and technology, learn to communicate, and try to find a way back home to his place in the sky.